How Living Things are Alike
Living things may be different in many ways, but they are alike
in important ways:
1. Every living thing on the earth came from another living thing. A snail's
parents are snails, and its young will be snails. They will grow and produce
more snails. A watermelon plant grew from the seed of another watermelon, and
its seeds can grow up to produce watermelon plants. These plants will produce
more watermelon plants. Living things reproduce living things of the same kind.
2. Living things are made of cells of protoplasm. Whales and oak trees, mice and
grass -- all are made of cells. A cell is a tiny package of living substances
which together are called protoplasm. Some of the protoplasm is in liquid
form, more or less like the white of an egg. Protoplasm consists mainly of
different kinds of proteins. Some of the protoplasm is the container part of the
package. It is called the cell membrane. Most cells have a part made of thick
protoplasm, called the nucleus.
3. Living things grow and change. Living things grow by increasing the number of
cells or the amount of protoplasm.
4. All living things need food. Living things use food as material for growth
and as fuel for energy.
5. All living things need oxygen. The oxygen is used by the cell in getting
energy from food.
6. Living things can move. The energy for movement comes from within the living
thing. It comes from food.
Nonliving things can move, too. A tin can may roll down a hill or be blown by
the wind. But the energy for this movement comes from outside.
Animals and Plants
After a scientist decides that a thing is living, he classifies
it as an animal or a plant. Plants resemble animals in many ways, but they are
different in these important ways:
1. Most plant cells have a thick, nonliving wall around the cell membrane.
2. Green plants can make food out of substances that are not food. In
photosynthesis green plants take in carbon dioxide and water to make food.
3. Most plants do not move very much or very fast, compared to animals. Plants
move when they grow. Stems grow and move up; roots grow and move down. Petals
move when flowers open and close.
In Between Animal and Plant
We have just divided the living things of the world into two
main groups -- plants and animals. But here again, everything does not fit.
There are tiny living things that can be classified as either plants or animals,
or neither. They are called euglena. After you find out more about
classifying plants and animals you might try to decide where you think they
belong, and why. Then look it up in an encyclopedia and find out what scientists
Plants - Discusses
energy & growth, flowers, other plants, and plant behavior.
Animals - Discusses Classifying
by Structure, How Scientists Classify, Vertebrates, and Invertebrates.
Insects - Discusses
how insects are alike, antennae, mouths, eyes, thorax, abdomen, how insects
grow, growing in 4 stages, growing in 3 stages, how insects survive, how
insects find each other, color that protects, insects that work together,
insect pests, and problems for scientists.